FORTUNE's annual ranking of America's leading businesswomen

As Facebook's No. 2, Sandberg was a central player in its high-profile -- and problematic -- IPO. She joined the board shortly after and is responsible for the company's moneymaking
strategy. Also on the board of Disney, Sandberg is a vocal advocate for young women at work. Expect a book on the subject in 2013.

From the October 8, 2012 issue

How we pick the Power 50

The list is compiled by FORTUNE editors, who consider four criteria: the size and importance of the woman's business in the global economy, the health and direction of the business, the
arc of the woman's career (resume and runway ahead), and societal and cultural influence.